Manufacture of copper sulphate



Aug. 2, 1932. P. J. F. SQUVHRON MANUFACTURE op COPPER SULPHATE Filed Dec. 5, 1929 Patented ug. 2, 1932 arrete* sr ras PIT-RRE JOSEPH FRANQOIS SOUVRON, OF TARBES, FRANCE MANUFCTURE OF COPPER S'LPI-IATE Application led December 5, 1929, Serial No. 411,945, and in France December 15, 1928.

The present invention relates to improvements in or relating to the manufacture of copper sulphate and provides a method and means whereby this substance can be manu- 5 factured more er'liciently and cheaply than hitherto.

It is known that copper sulphate can be obtained commercially by the simultaneous action on copper of air, water vapour and 10 sulphuric acid, all of which are contained in a closed vessel. in practice the operation is carried out by acting on granulated metallic copper by sulphuric aci-d ina large leaden tower through which is passed a current of l5 steam, air and acid, the agents being heated.

This process, however, suifers from the following disadvantages: l

l. The operation is extremely slow and necessitates introducing` a considerable quan- 21 tity of copper into the reacting towers, since it is estimated that one hundredth of the copper supplied is acted upon daily. It is the opinion of the applicants that the slowness of the reaction is due to the fact that this takes F place in a medium which is mainly gaseous.

2. rlhe process is costly, either by reason of the kcost of obtaining pure copper or, if pure copperis not used as a starting material, by

reason of the necessity for the metallurgical 'f operations for obtaining pure copper from the impure copper containing material.

3. It necessitates a considerable expenditure of heat for the production of the steam employed.

4r. The reaction product has to be removed from the tower and transported to a crystallizer.

5. Finally the apparatus is relatively complicated and cumbersome.

The present invention has for its object to provide a method and a means for the preparation of copper sulphate from rvery varying kinds of copper-containing materials, such as pure or impure copper, oXi-des', and the like, by means of a simple and economical plant into which the starting materals can be fed 5 to l0 times faster than in the old methods, and which give theoretical yields and facilitate the recovery of the secondary metals, that is to say, enabling considera-.ble reduction in costs. y

The method consists essentially in separating into two parts, both as regards time and place, the action on the copper and the solution of the product obtained, the first opera-- tion taking place in the cold in a liquid mediurn and the second one taking place without necessarily applying heat from outside. The effect is obtaned by transforming the copper into a salt which can readily be acted upon by sulphuric acid, for example by transforming the copper into copper oxychloride, which is insoluble in water but which dissolves in sulphuric acid with evolution of heat giving amixture of solutions of copper sulphate and copper chloride.

The formation of copper oxychloride from copper is effected by the action thereon in the presence of air of copper chloride, which simply serves as an intermediate product and is continuously regenerated, so that the production of the copper sulphate takes place more readily than hitherto and requires only the theoretical quantities of copper and sulphuric acid.

' The reactions which occur in the process are as follows:

and l It is pointed out that, owing to the ease with which copper oXychloride dissolves in sulphuric acid, the formation of copper sulphate can be effected in the crystallizers themselves. i

Vith this process can be prepared either crystallized copper sulphate CuSOiHQO in which case the respective quantities ofthe saltsemployed in the/reaction are so measured that the copper sulphate shall have the desired concentration for crystallizing out on cooling, or a solution of copper sulphate 'at any desired concentration if this is desired, as might be the case for example if the copper sulphate were required for the electrolytic production of copper. l

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As has been hereinbefore stated, copper sulphate can be obtained by this process without necessarily employing any external source of heat. If, however, it is desired to obtain copper sulphate of the usual commercial quality, and to obtain a greater yield at each crystallization, the temperature of the liquid mixture which is normally at about 45 CL55" may be raised to about 80G-90 quite simply by injecting steam directly into the crystallizer itself.

The operation can be carried out for eX- ample as follows:

In a large flat cement vat, which need not be lined with lead since theoretically it should not contain at any moment any free acid, are placed a number of perforated lead tubes connected to a fan and adapted to supply powerful currents of air through the contents of the vat at points distributed as much as possible throughout the vat. Copper for example, in the form of scrap metal, is introduced into the vat and the desired quan tity of copper chloride solution containing 150 grammes of CuCl2 per litre is added. This solution is further to contain at the end of the operation copper sulphate in such amount that is near to the point of satura' tion,

If it is desired to treat waste copper in powdered form (such as inillings, filings, cement copper etc), a number of frames of perforated wood are disposed in tiers in the vat and the material is placed on these frames.

Also the bottom of the vat may be so formed that a transverse section shows a series of saw-toothed grooves, the air tubes being deposited each at the bottom of a groove and along the length of the edge thereof. This arrangement has the advantage inter alia of causing the tubes to be covered with the material to be treated and of reducing the volume of the deposits between the tubes.

The mass is then traversed by a current of air when the copper is converted gradually into copper oxychloride in suspension in the liquid to which it gives a milky appearance.

The aeration is arrested as soon as the liquid has the desired content of oXychloride, which is then allowed to settle. After about l2 hours the precipitate of oXychloride is sufliciently settled to allow half of the total volume to be decanted as a clear liquid, This clear liquid which maybe drawn ofi' by means of a siphon for example is conducted to another reaction vat or into a reserve container.

The product remaining` in the reaction vat is then again agitated by air currents and drawn olf in turn by means of a siphon or pump to be conducted directly into a lead crystallizer provided if desired with plates of lead or copper suspended in the mass.

The just described method of operation is a discontinuous one.

It may be rendered continuous by the following improved method carried out in one of the two types of apparatuses shown on accompanying drawing:

Figs. l and 2 are a Vertical and a horizontal cross-section of an apparatus of the first type respectively and Figs. 3, 4 and 5 are a longitudinal, horizontal and transversal cross-section of an apparatus of the second type respectively. The former apparatus is more especially of advantage in the case where lump copper (wires, particles of refuse copper and the like) is used whereas the latter apparatus is better adapted for use with pulverulent copp-er (cement copper, filings and the like). The reaction vat preferably oVC concrete is divided in two parts by means of a partition l the top of which is a few centimeters lower than the normal level of the chloride solution 2, the larger of the two compartments 3 thus provided is arranged as described hereinabove i. e. it contains a wooden grating 8 carrying the copper-containing materi al 4L and the perforated lead blast pipes 5 fed through the air pipe 5 whereas the second smaller compartment 6 is empty at the outset and serves, vas will be explained hereinafter, as a reservoir for receiving the oirychloride formed 7. Owing to the stirring action pr vided by the incoming air in the liquid of the reaction vat, the copper oxychloride which forms as a suspension is brought to the surface and the greater part thereof passes into the smaller compartment with the li uid flowing into it under the action of the Cdifference between the levels in the two compartments produced by the blowing of air into the larger one. Suitable means are provided for extracting in a continuous or discontinuous manner the fluid oxychloride paste contained in the smaller compartment; but the process in the larger compartment is a continuous one.

In the cases where it is to be feared that a very light pulverulent material, such as certain precipitates may be carried out of the reaction vat proper into the reservoir compartment before the reaction is completely at an end, it is advantageous to provide between the two compartments i. e. the reaction vat and the reservoir, a third compartment forming a secondary reaction vat; air blowing pipes are then adapted to keep the material in suspension therein so as to allow the reaction to be brought to completion before the said material is allowed to pass into the reservoir where it deposes. Obviously no further raw material is fed into this intermediary compartment.

The second type of apparatus differs from that disclosed hereinabove solely by the following features. The wooden grating 8 carrying the raw material is disposed in tiers and the openings of each tier thereof is idisposed over the solid parts of the tier just underneath it. Moreover the walls of the compartment 3 show longitudinal in-dentations or corruga tions as shown on Fig. 5 at 9. Water may be admitted through the pipe 10 for removing the residuary mud from the reaction vat 3 into the receiver 12 through the cock 13 controlling the passage from the said vat into the said receiver.

A partition such as 14 (Figs. Sand 4C) may be provided with either type of apparatus to form the intermediary reaction vat mentioned hereinabove. Obviously it may be used with the lirst type of apparatus shown and it may be omitted in the second. A pump or .similar device 15 is advantageously disposed in the reservoir compartment 6 of either type for forcing the oxychloride formed into the lead crystallizers 16.

It is pointed out that in all cases the pro portions of copper, copper chloride and air must be carefully chosen, so that theI suspended oxychroride may thus be obtained in the form of a paste .sufficiently fluid to enable it to be readily conducted through the lead pipes by means of a siphon or pump.

The product is then again allowed to settle in the crystallizer for several hours, so that a further quantity of clear liquid can be drawn off.

This oxychloride is then treated with sulphuric acid at 60o or 66o B., for example, so as to be instantly converted in the crystallizer itself into copper sulphate and cupric chloride which is thus re-formed.

This addition of acid has the effect of raismg the temperature of the mixture to .lcec

C., this being due as much to the heat evolved by hydration of the concentrated acid as to that evolved by the chemical change of oxide into sulphate.

In practice sulphuric acid is added in excess of that necessary to obtain exact saturation, in amount such as to give an acid reaction with methyl orange.

Under these conditions the copper sulphate formed is present in a state of supersaturation, and a portion of it is precipitated in the form of sulphate snow, whilst another portion is precipitated later on cooling in the form of large crystals. If desired, the formation of sulphate snow may be avoided by reducing the amount of oXychloride so as not to exceed the point of saturation in the crystallizer. In this case, however, the volumetric yield is diminished, the rise of temperature being less pronounced.

lf it is desired, for reasons hereinbefore mentioned to raise the temperature of the mixture to about 900, it is only necessary to introduce into the crystallizer a lead tube for injection of steam without necessarily employing a coiled pipe which renders difficult the removal of the crystals deposited at the bottom of the crystallizer and considerably increases the costs of each crystallization.

After cooling the liquids in the crystallizersj Vthe mother liquors, saturated with copper sulphate, and containing the regenerated copper chloride, are again introduced into the reaction vats. The chloride employed can thus be used indefinitely except handling and transporting losses which are negligible.

The crystals deposited in the crystallizer are removed, washed, dried and sorted by any known and/ or suitableV means. Experience shows amongst other things that the presence of chloride of copper in the mother liquors does not in any way influence the quantity or appearance of the crystals ob tained.

The chief advantages of this method of manufacture are as follows 1. It is possible to obtain copper sulphate, the only materials expended being sulphur-ic acid and metallic `copper which need not be pure without its Vbeing necessary to carry out any preliminary metallurgical operation on the copper or to apply heat in carrying out the reaction.

2. The reaction is very much more rapid and requires a very much simpler apparatus thlan is the case with hitherto known methoc s.

3. The reaction is produced by a liquor which doesnot contain free acid, thus permitting the reaction to take place in cement vessels without a lead lining.

4. The handling is extremely simple since the materials are transported by siphons or pipes right up to the crystallization stage.

5. It is possible to produce the copper sulphate in the crystallizers themselves.

6. It is possible to obtain crystallized copper sulphate without any heating or with a very much reduced heating produced by direct injection of steam into the crystallizer.

Whilst a preferred method of carrying out this invention has been hereinbefore described, it will be understood that various modifications may be made without departing from the scope of this invention.

lWhat l claim is:

1. A closed circuit process for the preparation of copper sulphate consisting in treating metallic copper with a solution of cupric chloride, submitting the cuprous chloride formed to the action of air, treating the copper oxychloride formed with sulphuric acid,

precipitating the excess of copper sulphate formed and treating fresh copper with the mother liquor constituted by a solution of cupric chloride and copper sulphate.

2. A closed circuit process for the preparation of copper sulphate consisting in treating metallic copper waste with a solution of cupric chloride, submitting the cuprous chloride formed to the action of air, treating the copper oXychloride formed with sulphuric acid, precipitating the excess of copper sulphate formed and treating fresh copper Waste Lard Cil

with the mother liquor constituted by a solution of cupric chloride and copper sulphate.

3. A Closed circuit process for the preparation of copper sulphate consisting in treating metallic copper With a solution of cupric chloride, submitting the cuprous chloride formed to the action of air, treating the copper oxychloride formed With concentrated sulphuric acid, precipitating the excess of copper sulphate formed and treating fresh copper with the mother liquor constituted by a solution of cupric chloride and copper sulphatc.

4. A closed circuit process for the preparation of copper sulphate consisting in treating metallic copper with a solution of cupric chloride, submitting the cuprous chloride formed to the action of air, treating the comparatively Huid copper oxychloride formed with sulphuric acid, precipitating the excess of copper sulphate formed and treating fresh copper with the mother liquor constituted by a solution of cupric chloride and copper sulphate.

5. In the process claimed in claim l the step consisting` in heating the reacting mixture of copper oxychloride and sulphuric acid.

In testimony whereof I have aiiixed my signature.

PIERRE JOSEPH FRANCOIS SOUVIRON. 

